1. Field of the Invention
This invention relates to a spider assembly for the rotary hammer assembly of a hammermill and more particularly, to a replaceable end member for each arm of the spider.
2. Description of the Prior Art
Hammermills of the type contemplated herein include a rotary hammer assembly that has a number of spiders mounted on a shaft with hammers mounted for rotary motion between the arms of the spiders. During operation of the hammermill, the hammer assembly is rotated continuously to allow the hammers to swing past stationary combs and grate bars to impinge upon and fragmentize the metal objects fed into the mill.
To be effective, the orbit of the hammers must be quite close to the combs and grate bars with the extremities of the spiders actively involved in the fragmentizing action. As a result, the outer end portions of the spider arms are subjected to severe wear. In order to protect the tips of the spider arms, protective caps or tips are provided to protect the impact area on the lead edge of the spider arm. While the concept of protecting the ends of the spider arms with such tips or caps is not new, it has been found that the end of the spider arms, particularly the side walls, are also subjected to severe damage in the fragmentizing action. If the spiders are not replaced, the connections between the spider arms and hammers is weakened.
In order to repair the end of the spider arms, the spiders must be removed from the hammermill, thus causing shut down and considerable time loss and a reduction in the efficiency of operation due to the time required to dismantle the hammermill and replace the spiders.
A number of devices have been developed to protect the rotating parts of hammermill assemblies as a result of the impact of the rotating parts with the metal objects to be fragmentized in the hammermill. In Ratkowski U.S. Pat. No. 3,367,585 entitled "Replaceable Tip Member for a Two-Part Hammer" and Hightower U.S. Pat. No. 3,844,494 entitled "Hammer Mill Rotor Assembly" the problem of severe wear to the hammers was solved by providing a replaceable tip member on the hammer. In the '585 patent, a replaceable tip member is provided on the end of the hammer. In the '494 patent, heavy hammers were mounted on the forward portion of the spider. When the replaceable tip member became worn the pivot axis of the hammer was moved from the leading edge of the spider to the center of the spider. A cap was then mounted on the spider to protect the impact area of the spider.
In the Whitney U.S. Pat. No. 4,290,545 entitled "Method of Attaching A Protective Cap to a Shredder Component" the end disks on the hammer assembly are provided with a protective cap which is secured to the outer edge of the disk to protect the inside surface of the disk from impact by fragmentized metal objects.
In the Francis U.S. Pat. No. 3,727,848 entitled "Hammer Mill with Replaceable Spider Arm Tips" a replaceable tip or cap is disclosed which is mounted on the leading edge of the outer end of the spider to protect the spider from impact damage from the fragmentized metal objects.